In this day and age, ecology is a high priority item. Where in years past many remnant waste products from industrial operations were indiscriminately discharged into the atmosphere, water, or land dumps, every effort is made today to dispose of such waste products in an ecologically acceptable manner. In doing so, some benefits have been realized. For example, the cellulosic scrap from papermaking or lumber operations used to be left lying at industrial sites in ugly, polluting piles. Today, one economical way to dispose of these waste cellulose products is to burn them, using the heat to generate steam in a steam generator.
In many papermaking or lumber operations, there is insufficient waste product produced to keep a steam generator continuously operating. Or an operation may be seasonal, shutting down or being greatly curtailed during certain periods of the year. In contrast, the efficient use of the steam produced might require continuous and constant production. Thus, it is desirable to use some other fuel in addition to the cellulose waste, and be able to burn them singly or in combination. One such fuel that can be burned in conjunction with the cellulose fuel is crushed coal. The burning rate of crushed coal is generally much slower than that of cellulose waste products. In addition, the burning rate of various cellulose waste products can vary considerably. For example, large pieces of bark or woodchips take considerably longer to burn than sawdust or pieces of paper. Also, the moisture content greatly affects the burning rate. Thus, care must be taken in selecting the manner in which these various fuels can be most efficiently burned in conjunction with a second fuel, such as coal.